1. Field of Invention
This invention pertains to the art of methods and apparatuses for pumping fluid from a container to a delivery point in low volumes and at controlled flow rates, and more specifically to methods and apparatuses for using a piezoelectric driven pump to control the delivery of a fluid, such as a pharmaceutical solution or suspension, from a container to a delivery point.
2. Description of the Related Art
Numerous fluidics applications in such areas as medicine, chemistry, and environmental testing exist on a small scale for reasons of sample size, reagent costs, or portability. Cost-effective fluidics components, including pumps, that are capable and reliable are required for such small scale systems. Current pump designs are typically based on valves that open and close. Such valves tend to be direct applications of designs that work in macroscopic apparatuses, but are not necessarily the best choice for microapplications. These apparatuses require valve seats or other types of sealing and anti-seizure mechanisms, and typically are limited to fully-opened clearances that are relatively small.
A number of micropumps exist for delivering small amounts of a fluid to a delivery point. Some of the pumps include a piezoelectric element, which changes its dimensions when it is stressed electrically by a voltage. U.S. Pat. No. 4,938,742 to Smits describes a micropump with piezoelectric valves. These valves contain a diaphragm covered by a single layer of piezoelectric material, which limits the control and deflection possibilities of the valves.
U.S. Pat. No. 5,611,676 to Ooumi et al. shows the use of a cantilevered piezoelectric bimorph. A piezoelectric bimorph has two layers of a piezoelectric material separated by a shim. The application of an electric field across the two layers of the bimorph causes one layer to expand while the other contracts. The net result is a curvature much greater that the length or thickness deformation of the individual layers. However, the micropump of Ooumi et al. uses the piezoelectric bimorphs only as single function seals for opening and closing openings or as single function pumps, not as multifunctional seals and pumps.
The present invention contemplates a new and improved piezoelectric micropump that is simple in design, effective in use and compact. The new and improved piezoelectric micropump provides increased fluid flow rates with low power consumption. It overcomes the foregoing difficulties and others while providing better and more advantageous overall results.
In accordance with the present invention, a new and improved piezoelectric micropump is provided that pumps fluid from a container to a delivery point in small and precise amounts or at controlled flow rates.
According to one aspect of the present invention, a micropump for pumping a fluid from a fluid container to a delivery point is disclosed that includes a pump body. A passageway extends through the pump body from the fluid container to the delivery point. The pump body has first, second, and third cavities intersecting with the passageway. A first diaphragm covers the first cavity and opens and closes the passageway as the first diaphragm is raised and lowered. A first diaphragm clamp secures the first diaphragm to the pump body. A first cantilevered piezoelectric actuator raises and lowers the first diaphragm. The first cantilevered piezoelectric actuator has a first end and second end, the first end being operatively connected to the first diaphragm. A first actuator clamp secures the second end of the first cantilevered piezoelectric actuator to the pump body. A second diaphragm covers the second cavity and opens and closes the passageway as the second diaphragm is raised and lowered. A second diaphragm clamp secures the second diaphragm to the pump body. A second cantilevered piezoelectric actuator raises and lowers the second diaphragm. The second cantilevered piezoelectric actuator has a first end and second end, the first end being operatively connected to the second diaphragm. A second actuator clamp secures the second end of the second cantilevered piezoelectric actuator to the pump body. A third diaphragm covers the third cavity. The third diaphragm opens and closes the passageway as the third diaphragm is raised and lowered. The third diaphragm is secured to the pump body by the first diaphragm clamp. A third cantilevered piezoelectric actuator raises and lowers the third diaphragm. The third cantilevered piezoelectric actuator has a first end and second end, the A first end being operatively connected to the third diaphragm, the second end of the third cantilevered piezoelectric actuator being secured to the pump body by the first actuator clamp. An electronic control circuit supplies voltages to the first, second, and third cantilevered piezoelectric actuators for raising and lowering the first, second, and third diaphragms at predetermined intervals, thereby promoting a flow of the fluid through the passageway.
According to another aspect of the present invention, a micropump for pumping a fluid from a fluid container to a delivery point is disclosed which includes a pump body having a passageway therethrough from the fluid container to the delivery point. The pump body has first and second cavities intersecting with the passageway. A first diaphragm covers the first cavity. The first piezoelectric actuator has a first end and second end, the first end being operatively connected to the first diaphragm. The first diaphragm opens and closes the passageway as the first diaphragm is raised and lowered in response to a first piezoelectric actuator. A second diaphragm covers the second cavity. The second diaphragm opens and closes the passageway as the second diaphragm is raised and lowered. A securing apparatus secures the first and second diaphragms to the pump body. A second piezoelectric actuator raises and lowers the second diaphragm. The second piezoelectric actuator has a first end and second end, the first end being operatively connected to the second diaphragm. The second ends of the first and second piezoelectric actuators are secured to the pump body with the first ends of the actuators being cantilevered from the pump body. An electrical apparatus applies voltages to the first and second piezoelectric actuators causing the first and second piezoelectric actuators to raise and lower the first and second diaphragms at predetermined intervals.
According to another aspect of the present invention, the micropump pump body has a third cavity intersecting with the passageway. The micropump further includes a third diaphragm covering the third cavity. The third diaphragm opens and closes the passageway as the third diaphragm is raised and lowered. The third diaphragm is secured to the pump body by the securing apparatus. A third piezoelectric actuator raises and lowers the third diaphragm. The third piezoelectric actuator has a first end and second end, the first end being operatively connected to the third diaphragm. The second end of the third piezoelectric actuator is secured to the pump body by the cantilever securing apparatus. The electrical apparatus applies a voltage to the third piezoelectric actuator causing the third piezoelectric actuator to raise and lower the third diaphragm.
According to another aspect of the present invention, a micropump for pumping a fluid from a fluid container to a delivery point is disclosed which includes a pump body. The pump body has a passageway therethrough from the fluid container to the delivery point. The pump body has first and second cavities intersecting with the passageway. A first pumping apparatus opens and closes the passageway at the first cavity and creates a vacuum for promoting the flow of the fluid through the passageway. A first piezoelectric actuator actuates the first pumping apparatus. A second pumping apparatus opens and closes the passageway at the second cavity and creates a vacuum for promoting the flow of the fluid through the passageway. A second piezoelectric actuator actuates the second pumping apparatus. An electrical apparatus applies voltages to the first and second piezoelectric actuators causing the first and second piezoelectric actuators to actuate the first and second pumping apparatuses.
According to another aspect of the present invention, the pump body has a third cavity intersecting with the passageway. The micropump further includes a third pumping apparatus that opens and closes the passageway at the third cavity and creates a vacuum for promoting the flow of the fluid through the passageway. A third piezoelectric actuator actuates the third pumping apparatus. The electrical apparatus applies a voltage to the third piezoelectric actuator causing the third piezoelectric actuator to actuate the third pumping apparatus.
According to another aspect of the present invention, a micropump for pumping a fluid from a fluid container to a delivery point is disclosed. The micropump has a pump a body having a passageway therethrough from the fluid container to the delivery point and first and second cavities intersecting with the passageway. The micropump includes first and second diaphragms covering the first and second cavities, respectively. The micropump further includes first and second piezoelectric actuators each having a first end and second end. The first ends of the actuators are operatively connected to the corresponding diaphragms and the second ends are connected to the pump body to define cantilever supports for the diaphragms. The pump also includes a power supply for selectively applying voltages to each of the first and second piezoelectric actuators, causing said first and second piezoelectric actuators to raise and lower the corresponding diaphragms. The first and second diaphragms each open and close the passageway as they are raised and lowered by the piezoelectric actuators.
The piezoelectric actuators in the above-described micropump may be piezoelectric bimorphs. In such a pump, the actuation of the first and second diaphragms controls both pumping and valving.
According to another aspect of the invention, a micropump for pumping a fluid from a fluid container to a delivery point is disclosed. The micropump has a pump body having a passageway therethrough from the fluid container to the delivery point and first and second cavities intersecting with the passageway. The micropump includes first and second diaphragms covering the first and second cavities, respectively. The micropump further includes first and second piezoelectric bimorphs each having first and second ends. The first ends are operatively connected to the first and second diaphragms, respectively, and the second ends are connected to the pump body. The micropump also includes a power supply for selectively applying voltages to each of the first and second piezoelectric actuators to raise and lower the corresponding diaphragms. The first and second diaphragms each open and close the passageway as they are raised and lowered by the piezoelectric actuators. Application of a voltage to the first piezoelectric actuator displaces the first diaphragm to define a first reservoir in the first cavity and draw fluid from the container through the inlet and into the first reservoir and application of an opposing voltage to the first piezoelectric actuator displaces the first diaphragm in an opposite direction to force fluid in the first reservoir into the passageway downstream from the first reservoir and seal the first cavity.
According to yet another aspect of the invention, application of a voltage to the second piezoelectric actuator in the above-described micropump displaces the second diaphragm to define a second reservoir in the second cavity and draw fluid from the passageway downstream of the first reservoir into the second reservoir and application of an opposing voltage to the second piezoelectric actuator displaces the second diaphragm in an opposite direction to force fluid in the second reservoir into the passageway downstream from the second reservoir and seal the second cavity.
According to another aspect of the present invention, a method of pumping a fluid from a container to a delivery point through a micropump is disclosed. The micropump includes a pump body having a passageway therethrough and first and second cavities intersecting the passageway, first and second diaphragms covering the first and second cavities, and first and second piezoelectric actuators cantilevered between the pump body and the first and second diaphragms to raise and lower the first and second diaphragms. The method includes the steps of actuating the first piezoelectric actuator to raise the first diaphragm, thereby allowing fluid to flow through the passageway from the container to the first cavity; actuating the second piezoelectric actuator to raise the second diaphragm and actuating the first piezoelectric actuator to lower the first diaphragm, thereby allowing fluid to flow through the passageway from the first cavity to the second cavity; and actuating the second piezoelectric actuator to lower the second diaphragm, thereby allowing fluid to flow through the passageway toward the delivery point.
According to another aspect of the present invention, the pump body has a third cavity intersecting the passageway and the micropump further includes a third diaphragm covering the third cavity and a third piezoelectric actuator for raising and lowering the third diaphragm. The method further includes the steps of actuating the third piezoelectric actuator to raise the third diaphragm while actuating the second piezoelectric actuator to lower the second diaphragm, thereby allowing fluid to flow through the passageway from the second cavity to the third cavity; and actuating the third piezoelectric actuator to lower the third diaphragm, thereby allowing fluid to flow through the passageway toward the delivery point.
One advantage of the present invention is that the micropump controls the flow of precise amounts of fluid, which is particularly advantageous for pharmaceuticals and other fluids to be dispensed in precise amounts or at controlled rates.
Another advantage of the present invention is that each of the piezoelectric actuator and diaphragm assemblies acts both a gate for the passageway of the micropump and a pump promoting the flow of the fluid through the micropump.
Another advantage of the present invention is that the flow rate of fluid may be controlled by varying the level of voltage applied to the piezoelectric actuators, thereby controlling the amount of deflection and the level to which the diaphragms are raised.
Another advantage of the present invention is that the flow rate of fluid may be controlled by varying the frequency of the pumping cycle of the piezoelectric actuators.
Another advantage of the present invention is that the gradual application of an increasing or decreasing voltage to the piezoelectric actuators stabilizes the flow of fluid through the micropump.
Another advantage of the present invention is that cantilevering the piezoelectric actuators between the pump body and the diaphragms provides increased deflection of the diaphragms compared with piezoelectric circular disks to maximize fluid flow while controlling power consumption.
Still other benefits and advantages of the invention will become apparent to those skilled in the art to which it pertains upon a reading and understanding of the following detailed specification.